Greetings all, I have a Taxi that I bought in rough shape at an estate sale. It was sitting in a damp, detached brick garage with significant moisture issues. It barely did much when I first brought it home. I've gotten it to the point where I can play a game on it now. It seems like all of the play field features are functional, and the displays and scoring seem OK. However, only the left half of the the GI lights on the play field were working. During the troubleshooting for this, I found that much of the small relay board under the play field (labeled as 'RlyBd Sol. 11' in the Taxi manual) and its connector was burned/melted. I replaced the relay board and molex connector with a new ones from Marco, but now none of the play field GI lights are working.

I'm still a novice at reading schematics, so I'm not sure where to go with troubleshooting this. I've checked the 4 GI fuses on the backbox interconnect board. Can someone point me in the right direction? What kind of voltages should be present on the pins to the PF relay board? What's the best way to check the ground? What else can I check?

Thanks in advance.

Thanks for the quick reply, wayout. The lights did not come on when I grounded the brn-orn wire, so I'm leaning towards the relay board not getting power. I'm thinking this way because it's a brand new relay board. Which wire should be feeding voltage to the relay board, and how much? The picture you provided mentions 25V. Should that be present to the RB? If it is getting power, how can I check the relay itself?

I measured the brn-orn and the red wires to the RB (labeled DRV and PWR) and both measured between 41-43V DC. Is this good or bad?

By the way, was that image from the taxi manual? Or is there another resource for schematics for this system11b pin?

I really appreciate the help.

I just checked the yellow wires on the relay board for AC voltage- both were around 200 mV. So it seems that I'm not getting voltage to the relay board. I found a source for your earlier image here:

http://mirror2.ipdb.org/files/2505/Williams_1988_Taxi_Schematics.pdf.

I'm going to check what I can on these schematics, but I could still use a nudge in the right direction if you get the chance.

Thanks again wayout!

I think I found something. I used both of the exposed leads stapled to the underside of the play field, feeding the GI lamps, in turn for my tests of the voltage on the play field GI relay board. If I used the braided ground in the backbox instead, I got the readings that I think I expected- 4 of the pins read 24VDC and 2 read 72VDC. Was I right to expect one of the two stapled leads for the GI lamps to provide the ground? Does this suggest that I have a bad play field ground? What's the best way to test/troubleshoot such a scenario?

I think I may have a problem with my transformer

Out of the backbox interconnect board, on 2J7, I see 4.2 VAC on pins 9 and 10, but only 2.0 VAC on pins 7 and 8. This goes to the backbox GI, and seems to be working properly. However, on 2J9, I only measure 2.0 VAC on all 4 pins. Following it a bit upstream, I checked the input side of the backboard connect box, 2J6, pins 1-4 measured 2.0 VAC, and pins 6-9 measured 4.5 VAC. A little further up, I pulled the connector near the transformer and measured 4.5 VAC on the yellow pins, and 2.0 VAC on the yellow-white. The schematic seems to indicate 5.9 VAC should be here. Is there anything else I can check? Or should I start looking for a transformer?

Thanks again for all your help to get me this far!

Thanks all! Fortunately, once wayout set me straight on how to measure AC, I determined that my transformer seems to be working properly. The GI connectors were atrocious. Half of the molex connector was black and melted. I replaced 2P9 a long time ago, and didn't realize until late yesterday that I reversed the wire connections in the 2P9 molex connector when I replaced it.

So, after all that, it was completely operator error. Thanks to everyone that helped me learn more about troubleshooting. I was able to play a few games with a fully illuminated PF, now both flippers, 3 pop bumpers, and 2 of the kick bumpers stopped working...

Thanks again, wayout. Leaving a connector off seems (a) feasible since these specific solenoids were all affected at the same time and (b) it seems like something I would do. The selection of page 80 of the schematic that you posted above shows connector 5P12, which shows the affected features, and then points to 2P5 and 2P8.

2P5 pins 2 and 3 seem to be correctly aligned and secure with BLU-YEL and GRY-YEL, respectively. 2P8 pins 8 and 9 seem to be correctly aligned and secure with GRY-YEL and BLU-YEL, respectively.

I did some continuity testing on the ground side of the flipper, but made it all the way to 1P19 pins 1 and 2 successfully before not knowing where to go next. It seems to point to the K1 relay on the CPU board, but I'm not sure how to test that. It has to be removed to test properly, eh? Can you point me in the right direction?

I did notice that 2P5 pin 11 was a crappy punch-down and wasn't connecting securely to the pin, but I made that connection more secure and it seems to be testing properly now. Where does 2J5 pin 11 go along the backbone interconnect board? I don't see that on the schematics yet.

I really appreciate everyone's help here.

I think I may have found something. There is an empty pin connector on the Aux Power Driver board- it's 5J9. I don't see it called out on page 80 of the schematic, but it seems like it's called out on page 76 showing 25V and 50V on 4 wires of the 7 pins. Am I reading the schematic correctly? Or is this unused?

I can't find that connector anywhere. I checked to see if it fell down the hole at the bottom of the backbox, and I don't see it when I left the play field either.

I just blew my F5 fuse when attempting to ground a terminal on the right flipper.

Taking a different tack, I measured 74VAC at each of the 3 terminals on the left flipper.

Sorry for the mixed signals I'm sending. I'm still confident that both flippers will not work, once I pick up some replacement fuses this afternoon on my way home from work. I hope to be able to confirm that later today. Can I also test for voltage at the special solenoids to help identify the fault here?

Also, what is the correct way to manually ground a flipper to see if it's working?

Thanks again for all of your help!

I'm a computer guy, so I'm very familiar with the 'split-half' style of troubleshooting. I'm ashamed that I hadn't thought to apply it to troubleshooting a pinball machine before now.

I didn't get to the electronics store yesterday, but picked up some 2A SB fuses on my way home today. I popped one in F5, and can confirm that I now have 74 VDC on all 3 terminals of both flippers. I checked the lower kick bumpers for voltage and also saw 74 VDC across both terminals. So it seems that I have a grounding issue.

** As a quick aside- is there an easy way to remember what is AC vs. what is DC when troubleshooting a pinball machine? It wouldn't surprise me if there are differences between manufacturers, but is there an easy way to remember what is what on a System 11 machine like mine? Are most things AC except for the main CPU board?

So it looks like I'm back onto a grounding issue, and I chased the connections all the way back to the K1 relay (I think). Is there a way to test this while it's on the board? Or should I just plan on replacing it?

I can hear relay activity in the backbox when I start a game, but I can't quite discern whether it's R1 on the aux power board, or the K1.

If you've got continuity back to the MPU from the cabinet switch, and you have already checked for continuity of operation of the cabinet switch

I just checked for the presence of 74 VDC on 1P19-1, and I get it whenever I depress either flipper button, so it seems that the flipper circuitry is good, right?

If I ground the YEL-BLU wire from the right flipper the the braided ground wire coming from the cabinet transformer as you describe above, I get a big spark. This is how I blew the F5 earlier. Am I testing it wrong?

I haven't said thanks in a few posts- wanted to let you know that I still really appreciate your help on this.